1. Field of the Invention
The present invention relates to a component including at least two semiconductor elements which are connected to one another via at least one structured connecting layer, at least two hermetically tightly sealed cavities, in which different defined internal pressures prevail, being formed between these two elements. At least one of those cavities is sealed by a circumferential bonding frame in the connecting layer. Moreover, the present invention relates to a method for manufacturing such a component.
2. Description of the Related Art
One important exemplary application for the components mentioned here are so-called IMUs (inertial measurement units) including a MEMS (microelectromechanical system) element which includes a rotation rate sensor component as well as an acceleration sensor component. The two sensor components are formed in the layer structure of the MEMS element and situated next to one another. They are capped with the aid of the second element in order to protect the sensor structures and to ensure defined pressure conditions for the respective sensor operation. Since rotation rate sensors and acceleration sensors are usually operated at different ambient pressures, an individual cap structure is provided in the second element for each sensor structure. In rotation rate sensors, a part of the sensor structure is driven resonantly. In order to keep the damping of the sensor structure preferably low, a preferably low internal pressure of approximately 1 mbar is set in the cavity of a rotation rate sensor element. The rotation rate sensor may then be operated even at a relatively low excitation voltage. In contrast thereto, the sensor structure of an acceleration sensor is to preferably not be excited to vibrations. For this reason, acceleration sensors are operated at a significantly higher internal pressure of typically 500 mbar.
The internal pressure which results within a cavity between two elements joined by bonding is a function of the ambient pressure at which the bonding process is carried out. For this reason, the implementation of cavities having a different internal pressure for the individual sensor components of a MEMS element requires special measures when the two, sensor components are to be capped only with another element and in one single bonding step.
This is the object on which US patent application publication 2012/0326248 A1 is based. In this publication, it is suggested, among other things, to provide, in the area of a cavity, one of the element surfaces to be joined with a getter material or an outgassing material which bonds or releases a defined amount of gas at a corresponding temperature treatment. In this way, a targeted decrease or increase of the internal pressure of the cavity is to be effectuated.
This procedure is problematic for multiple reasons. In practice, it has been found that the internal pressure in such a cavity often changes even after the sensor calibration, since the getter material post-getters or the outgassing material gasses out further. This ultimately results in a distortion of the measurement results. But the micromechanical sensor function is often also interfered with by the extraneous materials in the cavity. Material ruptures repeatedly occur in particular in getter layers. This results in individual particles breaking off, which settle in or at the sensor structure and whose mobility is limited.